Power operated rotary knives are widely used in meat processing facilities for meat cutting and trimming operations. Power operated rotary knives also have application in a variety of other industries where cutting and/or trimming operations need to be performed quickly and with less effort than would be the case if traditional manual cutting or trimming tools were used, e.g., long knives, scissors, nippers, etc. By way of example, power operated rotary knives may be effectively utilized for such diverse tasks as taxidermy; cutting and trimming of elastomeric or urethane foam for a variety of applications including vehicle seats; and tissue removal or debriding in connection with medical/surgical procedures and/or tissue recovery from a body of a human or animal donor.
Power operated rotary knives typically include a head assembly and a handle assembly. The handle assembly includes an elongated central core and a hand piece mounted on the elongated central core. The hand piece includes a gripping surface to be grasped by an operator or user to manipulate the power operated rotary knife. The elongated central core includes a distal end attachment structure for releasably securing the handle assembly to the head assembly.
The head assembly includes a rotary knife blade, a blade housing for rotatably supporting the rotary knife blade and a frame body. At a proximal end, the frame body includes a mating attachment structure that receives the distal end attachment structure of the handle assembly to releasably secure the handle and head assemblies. At a distal end, the frame body includes a mounting pedestal for detachably mounting the blade housing. The frame body also defines a cavity to support a gear train for rotatably driving the rotary knife blade. The frame member supports the hand grip which is grasped by an operator and used to manipulate the power operated rotary knife.
In some prior rotary knives, a thumb support or thumbpiece, offset from the hand piece gripping surface, was positioned between the hand piece and the frame body to allow an operator to more easily manipulate and apply greater torque to the rotary knife. Examples of such a thumb support for a power operated rotary knife are found in U.S. Pat. No. 5,230,154 to Decker et al. and U.S. Pat. No. 5,400,511 to Decker, both assigned to the assignee of the present application. Both U.S. Pat. No. 5,230,154 to Decker et al. and U.S. Pat. No. 5,400,511 to Decker are incorporated herein in their respective entireties by reference. Such prior thumb supports included a base portion and thumb supporting portion extending at an angle from the base portion. The base portion defined a cylindrical ring that was mounted to an annular boss of the head assembly. The thumb supporting portion included a thumb contacting surface which received the operator's thumb. When the rotary knife was assembled, typically the base portion of the thumb support was sandwiched or constrained between the handle assembly and the head assembly.
Such prior thumb supports were unitary, that is, the base portion and the thumb supporting portion were fabricated of a single piece of material. As such, the thumb supporting portion was permanently fixed with respect to the base portion. Once the base portion was positioned on the annular boss of the head assembly in a specific position, the orientation of the thumb supporting portion, including the angle and location of the thumb contacting surface, was similarly fixed with respect to gripping surface of the hand piece.
Such a configuration may be problematic when right-handed and left-handed operators used the same power operated rotary knife. As used herein, a right-handed operator is an operator who grips and wields a power operated rotary knife with his or her right hand, while a left-handed operator is an operator who grips and wields the power operated rotary knife with his or her left hand. In some prior thumb supports, a thumb support for a right-handed operator would have a thumb contacting surface extending to the left (when viewed from above the power operated rotary knife) with respect to a longitudinal axis of the handle assembly, while a thumb support for a left-handed operator would have a thumb contacting surface extending to the right (when viewed from above the power operated rotary knife) with respect to the handle assembly longitudinal axis. Thus, a thumb support appropriate for a right-handed operator would not be suitable for a left-handed operator and vice versa.
Certain prior thumb supports could be rotated between different rotational positions on the annular boss of the head assembly to change the position of the thumb support from left-handed to right-handed use. However, rotating such thumb supports between different rotational positions on the annular boss required disassembly of the handle assembly from the head assembly, resulting in downtime for the power operated rotary knife and the operator.
Prior thumb supports, while useful, were lacking in certain respects, including the ability to change the position of the thumb contact surface for use by, for example, right-handed and left-handed operators or by operators who had differing hand sizes or configurations. Further, an operator using a rotary knife, may wish to change the orientation of his or her thumb with respect to gripping surface of the hand piece depending on the particular cut or trimming process being performed with the rotary knife, the amount of torque the operator wishes to apply, or to simply change the position of his or her thumb to mitigate hand fatigue. Prior thumb supports did not permit the operator to change the relative position of the thumb supporting portion with respect to the base portion so as to permit changing the orientation of the thumb supporting surface with respect to gripping surface of the hand piece. Thus, what would be needed is a thumb support for a power operated rotary knife which provides relative pivoting adjustment of the thumb supporting portion of the thumb support with respect to the base portion so as to permit changing the orientation of the thumb supporting surface with respect to the gripping surface of the hand piece without the need for disassembly of the handle and head assemblies.